This invention relates to the control of reactants in chemical engineering systems. More particularly but not exclusively this invention relates to the control of burners such as multiple burner systems.
As used herein the expression multiple burner systems includes unitary apparatus such as furnaces, having a multiplicity of burners and, in addition, plant incorporating a multiplicity of burners for a plurality of separate but related apparatus, such as a plurality of shell boilers each of which is provided with twin burners and combustion chambers in which the flues are provided with trunking to a common exhaust stack.
For the reduction of pollution and for the economic efficiency of the operation of such multiple burner systems, it is desirable to control the burners at all levels of their firing so as to provide each burner with an air/fuel ratio at approximately stoichiometric or any other desired condition.
In practice, however, considerable problems arise in attempting to obtain control of individual burners, and waste gas analysis hitherto shows only the overall air/fuel ratio and not that of individual burners, so that a control system relating to the overall waste gas analysis has not, in practical terms, provided optimum conditions for any but a few burners out of the multiplicity.
In addition in the case of furnaces attempts to provide such an overall analysis control system have tended to lead to instability problems due to an interaction between the required furnace temperature control and the stoichiometric control loop.
It is an object of the present invention to overcome or at least significantly reduce the above mentioned problems.